Effects of Climate Change on Municipal Water Supplies

The Washington Department of Ecology's report on the economic impacts of climate change are inconclusive about the effects on municipal water supplies in eastern Washington. While no changes in total annual precipitation are expected, more will fall as rain during the winter months. This is due to an expected 2 F increase in average annual temperatures by 2020. By 2040, the average temperature increase is expected to be 3 F.

This will mean snowpack will melt earlier in the spring, which will increase the amount of water flowing into rivers and streams during the winter and early spring, but flows will decrease in the summer months.

Spokane, and much of eastern Washington, relies heavily on aquifers for the water supply. The study points out that the changes in snowpack melting will affect groundwater recharge, which is how the aquifers replenish. But the study stops short of any estimates as to the potential impact that it will have.

Spokane's Water Department website describes the Spokane Valley-Rathdrum Prairie Aquifer (commonly called the Rathdrum-Spokane Aquifer) as one of the most productive aquifers in the United States, with a total volume of about 10 tillion gallons.

The aquifer covers 332 square miles from eastern Washington to the Bitterroot Mountains, where considerably more precipitation falls (about 70 inches per year compared with about 17 inches in Spokane).

Since the Department of Ecology study only measured the impacts in Washington state, I am concerned the principal source of water for the Rathdrum-Spokane Aquifer was left out of the study.